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http://www.traylorchemical.com/images/faqs/phchart.jpg Most nutrients are highest and most toxins are lower at pH 5.5-7 Sumber: cahe.nmsu.edu/directory/.../Powerpoint/14%20Nov%20soil%20chem.ppt‎

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Relationships existing in mineral soils between pH and the availability of plant nutrients. A pH range of about 5.5 to 7.0 seems to be best to promote the availability of plant nutrients. In short, if the soil pH is suitably adjusted for phosphorus, the other plant nutrients, if present in adequate amounts, will be satisfactorily available in most cases. Sumber: cahe.nmsu.edu/directory/.../Powerpoint/14%20Nov%20soil%20chem.ppt‎

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Kemasaman Aktif acidity that is in solution (H + ) that is measured with a pH ‘specific ion’ electrode (best), color indicators, dyes, litmus papers. Includes Al +3 in solution that hydrolyzes to form H + and Al(OH) x species Relatively speaking, active acidity is only a small amount compared to reserve acidity Sumber: cahe.nmsu.edu/directory/.../Powerpoint/14%20Nov%20soil%20chem.ppt‎

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Iron staining is often a good indicator of disturbed acid sulfate soils. When acid sulfate soils are disturbed and undergo oxidization, the sulfuric acid produced mobilizes iron, aluminum and heavy metals present in the soil. Toxic amounts of dissolved iron can then be washed into waterways. This iron can precipitate when in contact with less acid water, such as rainwater or seawater. This results in a rust-colored iron oxide scum or ‘floc' which can smother vegetation and stain concrete and soil. Sumber: cahe.nmsu.edu/directory/.../Powerpoint/14%20Nov%20soil%20chem.ppt‎